Dermatoglyphic method of medical genetics

Содержание

Слайд 2

Introduction to dermatoglyphi

All too often when we teach genetics we limit ourselves

Introduction to dermatoglyphi All too often when we teach genetics we limit
to the “tried and true “ single gene traits and “shy away” from more complex forms of genetic inheritance. After, all it is difficult enough to explain Mendelian Laws without the added complexity of quantitative variations. Ironically, understanding the relationship between genetic information and phenotypic expression at the organism level has more to do with the interaction of many genes than it does to any one gene in isolation. Dermal ridges are an example of a trait that shows quantitative variation, is inherited, and is easily analysed in the teaching laboratory. Further,sophisticated mathematical treatments need not be applied to teach the relationship between polygenic inheritance and expression.

Слайд 3

Dermatoglyphi and development

Dermal ridges originates from fetal volar pads composed of

Dermatoglyphi and development Dermal ridges originates from fetal volar pads composed of
mesenchymal tissue starting at the sixth to seventh week of development. In general, small pads produce arches and larger pads produce loops or whorls. Lateral displacement of the volar pad creates asymmetry of the pattern. Ridges become visible at about 3 months and are completed by the sixth month of prenatal development.

Слайд 4

Fingerprinting

A fingerprint is an individual characteristic-
-no two have yet been found to

Fingerprinting A fingerprint is an individual characteristic- -no two have yet been
possess identical ridge characteristics.
Fingerprints will remain unchanged during an individual’s lifetime.

Слайд 5

Anatomy of the Fingerprint

Skin is composed of layers of cells.
Epidermis

Anatomy of the Fingerprint Skin is composed of layers of cells. Epidermis
(outer portion) and dermis as inner skin.
In a cross section- a boundary of cells separating the epidermis from the dermis is made up of dermal papillae-these determine the form and pattern of ridges on the surface.
Dermal papillae develop in the foetus and remain unchanged during life.

Слайд 6

Types of fingerprints

Types of fingerprints

Слайд 7

Sir William Hershel-1856

He was the first to use fingerprints.
An English Chief

Sir William Hershel-1856 He was the first to use fingerprints. An English
Magistrate in India who used fingerprints for native contracts.

Слайд 8

Sir Francis Galton-1888

Sir Francis Galton, a British anthropologist and a cousin of

Sir Francis Galton-1888 Sir Francis Galton, a British anthropologist and a cousin
Charles Darwin, began his observations of fingerprints as a means of identification in the 1880’s.
In 1892, he published his book, “Fingerprints”, establishing the individuality and permanence of fingerprints. The book included the first classification system for fingerprints.

Слайд 9

Delta

The ridge point nearest the type-line divergence is the DELTA.
-Triangular in

Delta The ridge point nearest the type-line divergence is the DELTA. -Triangular
shape.
-ALL LOOPS HAVE ONE DELTA.

Слайд 10

Core

Core=center of the pattern

Core Core=center of the pattern

Слайд 11

Whorls

Whorls-4 distinct groups:
— Plain
— Central pocket
— Double loop
— Accidental
All whorl patterns

Whorls Whorls-4 distinct groups: — Plain — Central pocket — Double loop
have type lines and a minimum of two deltas.
Plain and central pocket loop whirl have at least one ridge that makes a complete circuit.
Ridge may be spiral, oval or any variant of a circle.

Слайд 12

Arches

Arches least common has 2 patterns- plain arches and tented.
Do not

Arches Arches least common has 2 patterns- plain arches and tented. Do
have:
—type lines
— deltas
— or cores

Слайд 13

Methods of detecting fingerprints

The method of choice will depend on the

Methods of detecting fingerprints The method of choice will depend on the
surface being lifted or tested.
Hard and non-absorbent surfaces (glass, mirror, tile, etc) require different approaches than soft and porous-paper, cloth, or cardboard.
The most challenging thing an examiner faces is finding the location of latent prints.

Слайд 14

Ultraviolet imaging systems

35mm black and white film.
Scene scope excels at

Ultraviolet imaging systems 35mm black and white film. Scene scope excels at
detecting prints on surfaces that a forensic light source would find difficult or impossible.

Слайд 15

Ninhydrin

The most cost effective chemical development method is Ninhydrin.
Ninhydrin is used

Ninhydrin The most cost effective chemical development method is Ninhydrin. Ninhydrin is
on paper, cardboard, or other porous surfaces.
The problem with spraying Ninhydrin solutions is that, since Ninhydrin reacts with amino acids, any exposure to your body, especially to your eyes or lungs, could have serious results. This potentially dangerous exposure is minimised by dipping or painting.

Слайд 16

Preservation of developed prints

Once visualised, it must be permanently preserved for

Preservation of developed prints Once visualised, it must be permanently preserved for
future comparisons and possible use in court as evidence.
Camera with close up lens.
Fixed focus to take photographs on 1:1 scale when lens is held exactly flush against the print surface to avoid distortion.
Photograph prints relative location with other evidential items.

Слайд 17

Permanent record of prints

If on small surface-transport without destroying the print.

Permanent record of prints If on small surface-transport without destroying the print.

Protect with cellophane bag.
If large surface objects that have been developed with a powder can best be preserved by lifting.
Done with broad adhesive tape.
Fingerprint covered with adhesive side and pulled up, the powder will be transferred to the tape.
Digital imaging may be used to enhance contrast, enlarge details and compare individual points on prints to others in question.